An ultrasound system has become an important and popular diagnostic tool since it has a wide range of applications. Specifically, due to its non-invasive and non-destructive nature, the ultrasound system has been extensively used in the medical profession. Modern high-performance ultrasound systems and techniques are commonly used to produce two or three-dimensional images of internal features of an object (e.g., human organs).
Generally, the ultrasound image is displayed in a Brightness-mode (B-mode) by using reflectivity caused by an acoustic impedance difference between the tissues of the target object. However, if the reflectivity of the target object is hardly different from those of the neighboring tissues such as tumor, cancer or the like, then it is not easy to recognize the target object in the B-mode image.
To resolve the problem of recognizing the tumor, cancer and the like in the B-mode, an ultrasound elastic imaging technology has been developed to visualize mechanical characteristics of the tissues such as the elasticity thereof in the ultrasound system. Such technology is very helpful for diagnosing lesions such as tumor and cancer, which are hardly recognized in the B-mode image. The ultrasound elastic imaging technology may utilize the scientific property that the elasticity of the tissues is related to a pathological phenomenon. For example, the tumor or cancer is relatively stiffer than the neighboring normal tissues. Thus, when stress is uniformly applied, a displacement of the tumor or cancer is typically smaller than those of the neighboring tissues. In order to form an elastic image, strains representing deformation of the tissues due to the application of the stress should be measured. The strains may be measured by using two ultrasound data obtained before and after compressing the tissues.
Further, the ultrasound system may provide a color map, which maps strains to pseudo colors. The elastic image may be colored according to the color map so that the tissues in the elastic image may be distinguished from each other. The conventional ultrasound system may provide a color map, which is formed by previously set colors, regardless of a portion subject to examination that is formed as an elastic image. For example, the conventional color map may be formed to map relatively large strains to a red color and relatively small strains to a black color. Thus, when the target object may include bones, fats, soft tissues and cancer tissues, a relatively soft portion, such as fats and soft tissues, may be mapped to the red color and a relatively hard portion, such as bones and cancer tissues, may be mapped to the black color. Thus, it may be difficult to separate boundaries and positions between the tissues.